Specifications

Product Technical Specification & Customer Design Guidelines
Noises and Design
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This document is the sole and exclusive property of WAVECOM. Not to be distributed or divulged without
prior written agreement.
WA_DEV_Q64_PTS_001-003 January 9, 2009
7 Noises and Design
7.1 Hardware and RF
7.1.1 EMC Recommendations
The EMC tests have to be performed as soon as possible on the application to detect
any possible problem.
When designing, special attention should be paid to:
• Possible spurious emission radiated by the application to the RF receiver in the
receiver band
• ESD protection is mandatory on all signals which have external accessibility
(typically human accessibility).
o Typically, ESD protection is mandatory for the:
 SIM (if accessible from outside)
• EMC protection on audio input/output (filters against 900MHz emissions)
• Biasing of the microphone inputs
• Length of the SIM interface lines (preferably <10cm)
• Ground plane: WAVECOM recommends having a common ground plane for
analog / digital / RF grounds and connecting to AREF (pin 60) for the audio
grounding.
• Metallic case or plastic casing with conductive paint are recommended
Note
:
The Wireless CPU
®
does not include any protection against overvoltage.
7.1.2 Power Supply
The power supply is one of the key issues in the design of a GSM terminal.
A weak power supply design could affect in particular:
• EMC performances.
• the emissions spectrum
• the phase error and frequency error
Warning:
Careful attention should be paid to:
• Quality of the power supply: low ripple, PFM or PSM systems should be avoided
(PWM converter preferred).